RDP Port Number TCP 3389
Need to know the RDP port number to open on your firewall? You’ll need to open up TCP 3389 to enable RDP or Remote Desktop services to pass through a firewall. By default most firewalls block the RDP port 3389 so if you are trying to RDP to a workstation or server on the other side of a firewall, make sure that the RDP port TCP 3389 is open.